Association between G6PD G202A Polymorphism and HbA1c among Patients with Type II Diabetes in Nigeria

Background: Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia. In hyperglycemic cases, haemoglobin binds irreversibly with glucose to form glycated haemoglobin (HbA1c) an accepted diagnostic test for type 2 diabetes mellitus (T2DM) used for monitoring glycaemic control in patients with diabetes. Some genetic variants influence the characteristics of HbA1c, via the erythrocytic pathway (erythrocytic variants), while some act through the glycemic pathway (glycemic variants). Glycemic variants increase the risk of developing diabetes, while erythrocytic variants have no association with the risk of diabetes. G202A, a variant of G6PD, is a single nucleotide polymorphism (SNP) associated with HbA1c in non-diabetic African Americans. G202A variant lowers HbA1c levels irrespective of an individual’s blood glucose level. Alterations in HbA1c caused by a G202A SNP of the G6PD in normal African Americans leads to a massive under-diagnosis of T2DM. There is no previous study on the effect of this SNP on HbA1c in diabetic individuals hence the need for this study. Methods: Thirty-two non-diabetic and 54 diabetic male adult subjects were recruited after signing informed consent. Venous blood was collected from which fasting blood glucose and glycated haemoglobin were measured.  DNA was extracted from whole blood. The samples were amplified, and amplicons digested using the PCR-RFLP technique and were visualised using a UV transilluminator. Data were analyzed using SPSS version 20 and SHEsis online software. Results: The genotypic distributions of G6PD G202A in the diabetic group were statistically significant (HWE p˂0.05). The minor allele frequency 202A was 20% and 16% in diabetics and non-diabetics, respectively. G6PD G202A polymorphism was associated with HbA1c in diabetic subjects. G6PD G202A SNP showed association with diabetes (p-value=0.003) and HbA1c in diabetic subjects. Conclusion: There is an association between HbA1c and G6PD G202A SNP in diabetic subjects.